Two-stroke cycle internal combustion engine with scavenging air blower



A. SCHEITERLEIN TWO-STROKE CYCLE INTERNAL COMBUSTION ENGINE WITH SCAVENGING AIR BLOWER Filed NOV. 28, 1956 June 23, 1959 INVENTOR fl. clzezterzem /ATTORNES United States Patent TWO-STROKE CYCLE INTERNAL COMBUSTION ENGINE WITH SCAVENGING AIR BLOWER Andreas Scheiterlein, Graz, Austria, assignor to Hans List, Graz, Austria Application November 28, 1956, Serial No. 624,793 Claims priority, application Austria December 13, 1955 1 Claim. (Cl. 123-65) For the purpose of improving the economy of operation of two-stroke internal combustion engines with fuel injection equipped with a scavenging air blower, a process is being used where part of the scavenging air is blown off when the engine is throttled. This process is known to reduce fuel consumption when the engine is operated at part load. However, the portion of scavenging air discharged into the open unnecessarily increases the power loss of the engine, since this portion of the air which has to be compressed and/or accelerated while passing through the blower, is lost for the combustion in the engine once it has emerged from the blower outlet. In order to avoid this loss it has already been suggested to return the portion of the compressed air not delivered to the engine cylinders into the suction chambers of the blower by means of a by-pass duct interconnecting the delivery and suction sides of the blower.

For the purpose of adapting the amount of air blown off or returned to the prevailing engine load, the by-pass duct contains a throttling member controlled according to the position of the regulating member of the injection pump and/or to the pressure in the connecting pipe between the blower and the scavenging air distributor.

It is the object of the invention to arrange the bypass duct and the throttling member in such a manner that especially when a Roots blower is used for the delivery of scavenging air, a dependable organ of easy manufac ture is obtained which can be readily attached to the crankcase as a self-contained unit. Whereas return ducts are known to have been cast integral with the sidewalls of the blower housing, yet such return ducts were either designed as angles or as sharp bends in an attempt to manage with a single undivided'housing and to provide for the direct opening of the return duct into the suction and exhaust chambers of the rotor housing. Such a run of the by-pass duct which according to a known suggestion leads to a semi-circular design of the duct, calls for complicated cores involving high manufacturing costs. This drawback is eliminated by the ingenious subdivision of the housing of the unit according to the invention.

The housing enclosing the rotors presents in a manner known per se two opposing, preferably even through surfaces, one of them serving for the attachment of the housing to the wall of the crankcase. On the opposite surface a cap-shaped closing means provides the interconnection between the outlet of the by-pass duct and the suction port of the rotor chamber. The entirely straight or only slightly curved by-pass duct runs essentially parallel with the line from the suction port to the outlet of the cavity of the blower housing destined to accommodate the rotor. The connection between the inlet of the by-pass duct and the outlet of the rotor chamber is provided by the crankcase, preferably by the air distributing chamber located inside the crankcase as with the known types of two-stroke engines.

The inlet pipe connection through which fresh air coming from an air filter is delivered to the blower, can be arranged inside the cap-shaped closing means.

According to a further embodiment of the invention,

the closing means may comprise a partition separating 5 said partition presenting an opening as known in conjunction with no-load valves of rotary compressors, the passage section of said opening depending on the position of the throttling member located in this instance in, the, f

cap-shaped member. a

The throttling member may be designed as a slide or valve. with the throttling member and closing the latter when the connection with the governor member of the injection pump is interrupted, prevent the throttling member from staying open in the event of failure of the injection pump to control the throttling member, causing damage to the engine. The real purpose of the spring means 13 which.

closes the throttling member 8 in the event of the connection between the throttling member and the fuel in-.

jection pump being interrupted is to ensure the operation of the engine at full speed even in the event of an interruption of the connection between the throttling member and the fuel injection pump. If the throttling member is in closed position, the engine will behave as if the arrangement according to the invention were nonexistent.

If no spring means 13 were provided, what might happen is that in case of an interruption of the connection be tween the throttling member and the fuel injection pump the throttling member will stay in open position, in which case the scavenging air blower would no longer'be caf pable of supplying the engine running at high speed with an adequate amount of air. I wish to point out that according to the invention the connection between the throttling member and the fuel injection pump is so de signed that as the amount of fuel injected and consequently the speed of the engine increases the throttling member 8 moves toward the closed position. With the engine running at full speed, the throttling member 8 is in completely closed position. This position is attained also in' the event of the linkage being interrupted, by the v pleted by the scavenging air distributing chamber of the l crankcase and equipped with a safety device protecting" the engine from damage such as above mentioned even in the event of a breakdown of the regulating mechanism.

The accompanying schematic drawing shows several embodiments illustrating additional features and further advantages of the object of the present invention.

Figure 1 shows a side elevation of an in-line engine with the Roots blower located on its side, partly in section along line II of Figure 2, and Figure 2 a section thereof along line II--II of Figure 1. Figure 3 shows another embodiment of the invention along the same line as in Figure 2.

Referring now in detail to the drawings it will be seen by reference to Figures 1 and 2 that the Roots blower 2 for the delivery of the scavenging air to the engine cylinders is located on the side of the crankcase 1. The air to be delivered to the individual cylinders via the scavenging air distributing chamber 2' emerges from the connecting pipe with the air filter (not shown) and enters the blower housing through the inlet of the suction stub 3. The inlet 3 and the outlet 6a of the scavenging air blower housing are interconnected by means of the by-pass duct 4 designed as part of the blower housing 2a. Owing to the location of the by-pass duct in the top wall of the blower housing it is possible for said by-pass duct to open directly into the air distributing chamber 2' prw Patented June 23, 1959 Springs acting upon a linkage connected vided in the crankcase. The resulting uniformity of the sealing surface 4a in addition to the plan shape of the housing which has to comprise only two ducts approximately parallel with each other, in which the air is compressed or returned respectively, and in conjunction with the surface 4b opposite the surface 4a which may also present an even through machining surface, is of particu lar advantage.

The outlet 5 of the by-pass duct 4 is located beside the suction port 6 of the blower housing and connected to same by means of a member 7 covering both openings cap-fashion and comprising a partition 7a serving for the separation of the by-pass duct from the suction chamher. The blown-off air is allowed to pass into the suction chamber of the blower through an aperture in said partition which can be closed by means of the throttling member 8. The adjustable throttling member can be used to regulate the amount of air to be blown off and returned. The throttling member is adjusted by means of a lever 9 connected to the governor lever of the injection pump 11 by means of a linkage 12.

It will be seen that the lever 9 is fixed on and projects radially from the rock shaft 8a which supports the throttling member or damper 8 for angular movement between open and closed positions in the port through the partition 7a. The rigid link 12 connects the free end of lever 9 to the free end of the governor lever 10, which is fixed on the rock shaft 10a which controls the fuel injection pump 11 so that the levers will move angularly together. The governor may be of conventional construction, the details of which are not pertinent and therefore are not shown. It will sufiice to bear in mind that the governor is arranged in any suitable manner to swing the levers 9 and 10 in a clockwise direction as viewed in Fig. 1, responsive to increases of speed of the engine and injection pump. At idling speeds and when the engine is not running, the governor so positions the lever arm 10 that it acts through the link 12 and lever 9 to maintain the damper open substantially as in Fig. 1. However, as the engine operates and its speed increases above idling speed the governor will rotate the levers 9 and 10 in a clockwise direction, as above mentioned.

In the event of a breakdown of this linkage, the throttling member is reset by means of a spring 13 to the position where the connection between the return duct and the suction chamber is interrupted. This is important in such cases where the connection between the injection pump and the throttling member is no longer operative. In that case, the engine might sufier damage if the throttling member were to stay in the position un- '4 covering the connection aperture between the return duct and the suction chamber.

In lieu of or in addition to the control of the throttling member by the governor lever of the injection pump as hereabove described, it is also possible to regulate the throttling member according to the pressure of the scavenging air at the outlet of the compressor and/ or in the scavening air distributor.

In order to reduce the width of the blower housing, the covering cap 7' can also be designed without a partition, the throttling member being located inside the return duct, as for example at the point marked 8' in Figure 3.

I claim:

A scavenging air blower for an internal combustion engine having an air distributing chamber operatively communicating with the cylinders thereof, a blower housing fixed to said engine, said housing having a blower passage communicating with said chamber, and formed with an air inlet port remote from said chamber, a blower in said passage between said chamber and said inlet port for delivering air into the chamber, said housing further being formed with a by-pass passage establishing communication between said chamber and said blower passage at a location on the remote side of said blower from the chamber, in combination with a damper movably dis posed in said by-pass passage to control the flow of air through said by-pass passage, a governor controlled by said engine responsive to the speed thereof and operatively connected to said damper to urge said damper toward closed position responsive to increase in the speed of the engine, and spring means resiliently urging the damper toward closed position.

References Cited in the file of this patent UNITED STATES PATENTS 1,031,245 Chapin July 2, 1912 1,646,373 Wilkin Oct. 18, 1927 1,898,460 Newcomb Feb. 21, 1933 2,037,402 Taylor Apr. 14, 1936 2,179,709 Brecht Nov. 14, 1939 2,384,282 Chandler Sept. 4, 1945 2,673,556 Reggio Mar. 30, 1954 FOREIGN PATENTS 635,823 France Jan. 3, 1928 507,690 Great Britain June 20, 1939 113,400 Sweden Mar. 6, 1945 837,488 Germany Apr. 28, 1952 

